Tales of modest investments producing major returns are common currency in today's financial markets, but not so familiar in the worlds of architecture and urban design.

What transpired in Greenbelt in recent years is thus eminently worth recounting. The story can be summed up in a few words: For about $200,000, the historic suburb saved its splendid New Deal core.

Unlike most stock market adventures, Greenbelt's happy ending was pretty much guaranteed. It took an educated, sensitive pair of eyes to see precisely what was wrong and how to fix it--in this case, eyes belonging to landscape architect Sharon Bradley-Papp.

Greenbelt's community-commercial hub was an integral part of the original layout of the mid-'30s suburb, one of three actually constructed by President Franklin D. Roosevelt's Resettlement Administration. (The others are in Ohio and Wisconsin.)

Indeed, the town center is one of the reasons why well-preserved Greenbelt remains one of the more inspired (and inspiring) achievements in American suburban planning of the last 100 years.

Architecturally, the original buildings of the aptly named Roosevelt Center shopping area are distinguished by their modest modernism. Two stories high, with rounded corners, industrial-style horizontal windows and bearing walls of white-painted brick, they exhibit in discreet measure the streamlined tendencies of advanced American architecture of the period. The movie house marquee, recently restored, is the only visual fanfare--and a rather low-key one at that.

Yet these commercial structures are, in their subtle way, brilliant. This is because they serve a larger purpose: They shape civic space.

The town center was the appropriate focus of a superb topographical layout. The main feature of the land--a long, curving, woodsy ridge--determined the parallel crescent shapes of Greenbelt's two main roads. Two-story row houses and three-story apartments were sensitively placed around and between the two roads. A generous system of pedestrian pathways circulates through open and forested public spaces between the homes. Ducking under the roadways for safety and convenience, the paths converge on the civic core.

With their streamlined curves and setbacks, the commercial buildings frame the rather intimate, rectangular civic plaza--the scale is definitively small town. Originally, the pathways continued gracefully down a knoll into the woods beyond, and then to a man-made lake.

(Much of this extension of the plan has been degraded and obscured by post-World War II additions--pathways remain, but they certainly are not graceful. Nor is the more recent architecture. But more on that in a moment. It is the unfinished part of Greenbelt's civic-center tale.)

Simplicity and openness characterized the original plaza design. There were four rectangular planting areas with shrubs and benches at the edges. A massive limestone statue of a stylized mother and child by Works Progress Administration artist Lenore Thomas formed a visual focus, symbolizing the sturdy spirit of the original families, who were given to calling themselves "pioneers."

In the mid-'70s, however, the open character of the plaza was transformed when the planting rectangles were replaced by a formal grove of Bradford pear trees. Residents welcomed the shade, but as the trees filled out, the plaza grew ever darker. By the mid-'80s the buildings, the statue and views into and out of the plaza were significantly obscured.

In effect, despite the shade and comfortable benches, the plaza had become a much less definable place. Neither its dimensions, its shape nor its historic period were any longer readily apparent.

Not surprisingly, as it became a sort of neutral zone, the Roosevelt Center's use as an informal community meeting place began to decline. On the other hand, drug dealers and other antisocial types were able to take advantage of the new design features. Greenbelt police found themselves devoting an inordinate amount of resources to the town center.

Bradley-Papp, among others, had been watching the deterioration with concern. She is a landscape architect with deep Greenbelt ties. Her grandparents on both sides were among the original "pioneer" families; her parents were reared in Greenbelt and, after getting married, moved only as far as nearby Riverdale. Bradley-Papp grew up with Greenbelt visits and stories; when she herself got married, it seemed a natural choice. She has lived in Greenbelt with her own family since 1985.

When the city announced its request for proposals to re-remodel the civic space five years ago, Bradley-Papp was more than ready. She knew that something of the original clarity had to be reestablished. This was important to the historic identity of the place and a key to driving away the bad guys.

At the same time, she knew that the pear trees and their shady undersides were viewed with great affection by many in the community. Persuading people to cut down the trees was not easy. In this campaign, however, Bradley-Papp was aided by the trees themselves. The Bradford pear, a beautiful hybrid specimen developed in the '60s, became an urban planting fad in the '70s. But it turned out to be a fragile, even dangerous fashion--as the trees age, they tend to split and fall.

As revived according to Bradley-Papp's design, the Roosevelt Center combines the openness and focus of the original, some of the shade that characterized the '70s plan and a dollop of contemporary liveliness. It is altogether unpretentious--and extremely successful.

New shade trees--zelkovas--were planted in a pattern that reinforces the sense of place. The mother-and-child statue, still undergoing repair by conservator Sharon Koehler, once again is visible in its central position. The buildings themselves--and in particular the renovated theater marquee unveiled last February--can again be seen as one approaches the center. Concrete-and-wood-beam benches, modeled after those of the '30s, provide respite in the shade. Awnings hover above tables surrounded by movable (but very heavy) chairs. Today's Roosevelt Center is new and improved, but it builds upon strengths of the past.

The same cannot be said for the rest of Greenbelt's center. Although immediately adjacent to the rear of the plaza, architectural additions of the '60s pretty much turned their backs on it. The original graceful pathways are gone, and their replacements are poorly designed and positioned.

Bradley-Papp has a plan to clear up at least part of this unfortunate mess. Phase 2 of her Roosevelt Center design, as yet unfunded, foresees improving the pathways and terracing the hillside behind the plaza to make it both more attractive and useful. (It could become a natural outdoor amphitheater for the adjacent performing arts center.) So far, so good, but Greenbelt also needs to do something about those helter-skelter parking lots.

This may be asking too much--after 65 years, the energy simply may not be there. Then again, inspiration is close at hand. As Bradley-Papp has demonstrated, we can all still learn from the innovative original Greenbelt plan, with its emphasis on affordability, public spaces and pedestrian circulation, and its sensitivity to nature.